The question "what kind of number is" can be answered by understanding the basic classifications or types of numbers in mathematics. Numbers are classified into various types including natural numbers, whole numbers, integers, rational numbers, irrational numbers, real numbers, imaginary numbers, and complex numbers.

• Natural numbers are counting numbers starting from 1, sometimes including 0.
• Whole numbers include all natural numbers plus zero.
• Integers include all whole numbers and their negative counterparts.
• Rational numbers are numbers that can be expressed as a fraction of two integers.
• Irrational numbers cannot be expressed as a simple fraction and have non-repeating, non-terminating decimal expansions.
• Real numbers include both rational and irrational numbers.
• Imaginary numbers involve the square root of negative numbers, represented by i where i2=−1i^2=-1i2=−1.
• Complex numbers are combinations of real and imaginary numbers, such as a+bia+bia+bi where aaa and bbb are real numbers.

Each of these categories represents different properties and uses within mathematics, and numbers can often fit into multiple categories, depending on their characteristics.